Watch Clarkson break down in the middle of a highly emotional number.

By Perri Ormont Blumberg
August 21, 2018
Jeff Kravitz/Getty Images

Wedding guests and newlyweds got a surprise for the books when Kelly Clarkson emerged from behind a curtain to sing the couple's first dance song, her 2015 single "Piece by Piece."

As the bride and groom took the dance floor for the special moment, Stacy, the bride, looked utterly shocked when she saw Clarkson on stage. The emotional duo danced as happy guests took on the spectacle in awe. "You didn't know she was going to be here?" Stacy asks her new husband at one point. "No. I swear to God," he replies.

Towards the end of the evocative song documenting Clarkson's personal struggles and triumphs with her absent father, she quivers, holding back tears, "It's hard to sing at a wedding."

So how did this big moment come to be? "Your sister Tanya set this all up. And she put it all together for they told me you related to this song. I thought, you know, might be a cool moment that you...found someone better maybe than what we were shown," Clarkson says, before running over to hug the bride. Watch below.

No further personal details were given about the couple or location of the wedding.

WATCH: You'll Never Guess What the Bridal Party Wore at This South Carolina Wedding

Personally, this reception shocker is one form of wedding crashing we'd certainly be A-OK with, considering how meaningful it was to the couple and their guests. Well done, Kelly.